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That was an excellent summary of the salient points of the Forum's longest thread.

Originally posted by Tom Loizeaux Can you tell me what the port sizes should be for the 4 cu. ft. and 5 cu.ft. boxes should be?
(using 3" and/or 4" tubes)

Thanks,

Tom

Tom,

To explore the two vented enclosures described above, you will need to build the cabinets so that the net volume is 4 or 5 cu ft. That means you have to add the volume of all of the bracing, the driver, and the port or ports. Typically it will add between 0.4 cu ft to 0.75 cu ft.

For a 4 cu ft cabinet tuned to 25Hz you could use a pair of 4" ducts at 22 3/8" long. (Might be tough to fit in the box.)

If you use one 4" tube it would be 9 9/16" long but at high spls it might make pumping noises.

You could construct a rectangular port of 4 1/4" by 4 1/4" by 14 7/16". This would be my choice.

For a 5 cu ft cabinet tuned to 21Hz you could use a pair of 4" ducts at 26" long. (Might be tough to fit in the box.)

If you use one 4" tube it would be 11 3/8" long but at high spls it might make pumping noises.

You could construct a rectangular port of 4 1/4" by 4 1/4" by 17 5/16". This would be my choice.

If you have the time and inclination you might take Giskard's advice and build a sealed box as well and compare them. I did as I had heard them set up that way in their original Revel enclosures and was impressed with them. I found for my needs and lust for ever more I opted for the 5 cu ft vented option. The bottom line is that with these woofers you can't go wrong.

L200 cabs as enclosure?

Does anyone know the volume of the L200 (L200 Studio Master Speaker Cabinet) I picked up a pair empty cabs on ebay and thought I might convert it for a sub1500 enclosure (temporarly to play with), and want to set up a vented enclosure (or maybe later sealed). Any hints or reactions welcome. I have been toying around with cutting out he back panel, pulling out the existing braces and building a box with 3/4 mdf inside it and bracing the crap out of it. (that is, if the original bracing doesnt look like it will handle these bad boys with out sending panels out toward my family during Independence Day landings) These seem to be in excellent condition and I love that Star Trek, 1970 look of the box. Reality checks encouraged.

l200/5foot enclosure vents

Thanks Tom, I calculated a little over 6 cubic feet but that was based on external published dimensions and I knew that couldnt be right.
Mr. Widget, what about using three ports in a five cubic feet enclosure, could I decrease the length of the vents, (like in my 4518 enclosure for my 2245h). I dont have box modeling software, but planned on trying the sub1500 in these L200 enclosures this weekend and thought I could throw another vent into the horn hole. I think the vents in the L200 are three inches, I could install three four inch ones, but dont know what depth. (obviously I would prefer to just have three of the ones in place but would probably have 24 inch port tubes).
Thanks, my wife is extremely excited about getting the pair of SUB1500s, and my brand new used Crown K2 pounding in our 150 ft2 living room ,
Oh well, its either speakers or the AV room addition, I dont have time for everything

Re: l200/5foot enclosure vents

Originally posted by andresohc
Mr. Widget, what about using three ports in a five cubic feet enclosure, could I decrease the length of the vents, (like in my 4518 enclosure for my 2245h).

Essentially as the area of the port increases the port length must increase to maintain the same tuning frequency. So if you use (1) 4" tube for 21Hz it is 11.3", (2) 4" tubes for 21Hz are each 26", (3) 4" tubes for 21Hz are each 41".

Now a hole cut into a 1" baffle with no tube would be a little under 1.75" in diameter. The problem with the smaller port diameters is that as they get smaller the likelihood of air moving through the port causing audible noise goes up.

Since JBL typically tunes in the 30Hz up range the ports are shorter in length.